Recently, advanced wireless communication devices, which are typically portable telephones, have a multiband system using multiple frequency bands used for communications and a systematization with various functions, and multiple wireless devices have been installed in one communication device. However, downsizing and thinning of the portable telephone have been continuously demanded, and downsizing and thinning of components installed therein have been strongly desired.
Further, there is a strong demand for cost reduction of the devices. Therefore, in many cases, multiple components are incorporated into a module to thus achieve downsizing and cost reduction in mounting the components.
Among the components installed in the wireless communication devices, an acoustic wave filter and a duplexer using such a filter are produced by a method quite different from that for producing semiconductor components. It is therefore difficult to integrate these components on the same substrate. Actually, the acoustic wave filter and the duplexer are mounted separately from the semiconductor components. However, multiband communications in one portable telephone use multiple acoustic wave filters and multiple duplexes suitable for the multiple frequency bands. For the purpose of downsizing and weight lighting, the multiple acoustic wave filters and duplexers should be incorporated into a single module, which is also to be downsized and thinned.
Now, there is a considerable activity in the development of modules in which acoustic wave filters and duplexers are incorporated. In order to downsize the module, the individual acoustic wave filters and duplexers should be arranged on a module substrate as close to each other as possible, and interconnections lines for interconnecting the duplexers should be as close to each other as possible. Further, the acoustic wave filters and the duplexers should be downsized. Therefore, many cases have close arrangements of interconnection lines that interconnect vibration elements in the acoustic wave filter elements and those for interconnecting the acoustic wave filters. The above-mentioned arrangements may raise the following problems. An unwanted electromagnetic coupling may increase between the lines for interconnecting the acoustic wave filters. Another unwanted electromagnetic coupling may increase between the interconnection lines in the module substrate. These unwanted electromagnetic couplings may degrade the rejection characteristics of the acoustic wave filters, and may degrade isolation between the duplexers.
As a problem raised by downsizing of the acoustic wave filters, it is known that a ripple occurs in the frequency characteristic of the pass band of the acoustic wave filter and increases the insertion loss. Japanese Patent Application Publication No. 2008-28826 (Document 1) proposes a structure directed to solving the problem.